This invention relates generally to a compressed air or pneumatic engine, and particularly to a piston type pneumatic engine in which the flow of compressed air to individual cylinders can be selectively interrupted.
In the known prior art, the speed and work output of the engine is controlled by the throttling of the flow of compressed air to the engine.
Many loads, currently driven by engines, are of the type which require a fairly high torque or work output of the engine to overcome inertia and put the load in motion. However, once the running speed of the load has been reached, the load has momentum requiring only a lesser amount of work to overcome frictional losses to keep the load moving. An example is an automobile which in operation requires more work out of its engine when accelerating to an operating speed than when traveling at the chosen operating speed.
In the known prior art pneumatic engines, commpressed air is supplied to each of the cylinders regardless of the operating speed and work required of the engine. When the engine is operating at high speeds, compressed air must be supplied to each of the cylinders even though the required torque or work output of the engine may be low. This represents an inefficiency or waste of energy as air which has been compressed by the expenditure of work is being utilized mainly to fill a void created by the displacement of the pistons as the engine turns. If the engine could be operated at a given higher speed requiring low torque output while utilizing less compressed air, the efficiency of the engine would be improved.